fix minor bugs

luprex/core/cpp/drivenengine.cpp

@@ -164,7 +164,7 @@ UniqueChannel DrivenEngine::new_incoming_channel() {
     } else {
         UniqueChannel result = std::move(accepted_channels_.back());
         accepted_channels_.pop_back();
-        return std::move(result);
+        return result;
     }
 }